Tapping the potential of Landsat archives for the monitoring of irrigated land use development in the lower Syr Darya catchment, Kazakhstan, 1984-2017

Kurzfassung

Agriculture is one of the economy priorities of Kazakhstan. After the collapse of the Soviet Union in 1991, the country had to cope with enormous transformation processes including land privatization and implementation of new organizational structures in agriculture. Together with the existing land degradation problems that negatively affected crop production, these processes led to land abandonment, e.g. in the downstream rice cropping systems along the Syr Darya River. However, potential solutions for a more sustainable production demand for more detailed information on the use of croplands over time. Therefore, a temporal transect of land use maps for the rice-dominated Kazalinsk region, Southwest Kazakhstan, was generated through a remote sensing and GIS analysis. We processed 84 images of different Landsat sensors recorded between 1984 and 2016. For the elaboration of the approach and for the verification of the maps ground data were collected in 2015 and 2016. Three temporal windows (early, mid, and end of season) and a simple but effective mapping approach permit the accurate identification of actively used rice fields. The results returned a remarkable decline of rice production area during the late Soviet Union era (annually, 17,000 ha out of entirely 38,444 ha were used for rice production) until 2004 (5,000 ha), which was followed by some re-use of cropland for rice production afterwards (~10,000 ha). Counting the number of years under rice production highlighted that compact blocks of rice production are more likely to be active than fragmented fields, which could be attributed to the costs required for irrigation under the risk of water scarcity. Next steps include the overlay of the land use indicators with GIS information such as the irrigation canal network, soil quality, soil salinity, and groundwater tables in order to model the mechanisms that led to variations in rice production, or land abandonment.